M&S says

This Maxim coffee mug boasts a simple, yet elegant design that’s guaranteed to freshen up your coffee moments. Created with StayNEW™ technology, this porcelain mug is dishwasher resistant so you can easily keep it clean, and its colours stay brighter for longer. For any formal or casual occasion, group this coffee mug with more from our matching Maxim range for a dining set that’s hugely functional and durable for everyday use, and looks stylish too.